首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   647篇
  免费   9篇
  国内免费   1篇
电工技术   1篇
化学工业   141篇
金属工艺   2篇
机械仪表   3篇
建筑科学   27篇
能源动力   1篇
轻工业   51篇
水利工程   3篇
无线电   17篇
一般工业技术   74篇
冶金工业   296篇
自动化技术   41篇
  2022年   6篇
  2021年   7篇
  2018年   6篇
  2014年   8篇
  2013年   14篇
  2012年   11篇
  2011年   32篇
  2010年   18篇
  2009年   17篇
  2008年   24篇
  2007年   37篇
  2006年   24篇
  2005年   22篇
  2004年   17篇
  2003年   12篇
  2002年   17篇
  2001年   18篇
  2000年   13篇
  1999年   8篇
  1998年   11篇
  1997年   16篇
  1996年   17篇
  1995年   10篇
  1994年   12篇
  1993年   16篇
  1992年   11篇
  1991年   5篇
  1990年   12篇
  1989年   14篇
  1988年   13篇
  1987年   11篇
  1986年   13篇
  1985年   9篇
  1984年   9篇
  1983年   9篇
  1982年   5篇
  1981年   7篇
  1979年   5篇
  1978年   9篇
  1977年   8篇
  1976年   9篇
  1975年   5篇
  1974年   7篇
  1973年   9篇
  1964年   4篇
  1963年   9篇
  1962年   11篇
  1961年   9篇
  1960年   12篇
  1959年   11篇
排序方式: 共有657条查询结果,搜索用时 15 毫秒
61.
The last decade has witnessed an extraordinary shift in housing policy in Canada. Responsibility for social housing has been devoluted from the federal government to theprovincial and territorial governments, who in turn shift administration and manangement to regional and municipal agencies. And while the proportion of needy families is increasing, the deficit-minded Federal government only maintains its financial commitments to existing projects with no new funds presently available. Market solutions are being promoted by both the public and private sectors through a wide range of activities. The result is no single housing policy, but a patchwork of provincial and local initiatives.  相似文献   
62.
A 28-day accumulation study demonstrated the use of mussel uptake, passive samplers, and biodynamic modeling to measure the reduction of dichlorodiphenyltrichloroethane (DDT) availability in the water column after the addition of activated carbon to contaminated sediment. Sediment collected from Lauritzen Channel, Richmond, California (16.5 mg total DDT/kg) was mixed with either virgin activated carbon or a reactivated carbon for one month, after which a 28-day laboratory exposure study was completed. Mussels (Mytilus edulis) suspended above activated carbon-treated sediment accumulated significantly less total DDT in soft tissue, 91% and 84% for virgin and reactivated carbon, respectively, as compared to untreated sediment. Mussel tissue concentrations correlated to concentrations in semipermeable membrane devices (SPMDs) and polyethylene devices (PEDs) suspended over the same sediments. A biodynamic model that incorporated DDT water concentrations, either analytically measured or estimated from PED uptake, described mussel accumulation over time. Thus, passive samplers in combination with biodynamic modeling may provide an important screening tool for assessment of filter-feeding uptake and ecological risk to water-dwelling organisms exposed to aqueous phase hydrophobic organic contaminants.  相似文献   
63.
We demonstrate two-dimensional multiplexed real-time, label-free antibody-antigen binding assays by optically detecting nanoscale motions of two-dimensional arrays of microcantilever beams. Prostate specific antigen (PSA) was assayed using antibodies covalently bound to one surface of the cantilevers by two different surface chemistries, while the nonreaction surfaces were passivated by poly(ethylene glycol)-silane. PSA as low as 1 ng/mL was detected while 2 mg/microl of bovine serum albumin induced only negligible deflection on the cantilevers.  相似文献   
64.
The purpose of our analysis was to determine if older adults show sleep inertia effects on performance at scheduled wake time, and whether these effects depend on circadian phase or sleep stage at awakening. Using the Digit Symbol Substitution Test, effects of sleep inertia on performance were assessed over the first 30 min after wake time on baseline days and when sleep was scheduled at different circadian phases. Mixed model analyses revealed that performance improved as time awake increased; that beginning levels of performance were poorest when wake time was scheduled to occur during the biological night; and that effects of sleep inertia on performance during the biological night were greater when awaking from non-REM (NREM) sleep than from REM sleep. Based on our current understanding of sleep inertia effects in young subjects, and previous reports that older subjects awaken at an earlier circadian phase and are more likely to have their final awakening from NREM sleep than younger adults, our findings suggest older adults may be more vulnerable to sleep inertia effects than young adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
66.
A method of analyzing Faraday rotation data from pulsed magnetic field measurements is described. The method uses direct least-squares elliptical fitting to measured data. The least-squares fit conic parameters are used to rotate, translate, and rescale the measured data. Interpretation of the transformed data provides improved accuracy and time-resolution characteristics compared with many existing methods of analyzing Faraday rotation data. The method is especially useful when linear birefringence is present at the input or output of the sensing medium, or when the relative angle of the polarizers used in analysis is not aligned with precision; under these circumstances the method is shown to return the analytically correct input signal. The method may be pertinent to other applications where analysis of Lissajous figures is required, such as the velocity interferometer system for any reflector (VISAR) diagnostics. The entire algorithm is fully automated and requires no user interaction. An example of algorithm execution is shown, using data from a fiber-based Faraday rotation sensor on a capacitive discharge experiment.  相似文献   
67.
The hydrothermal deep-sea vent fauna is naturally exposed to a highly specific environment enriched in potentially toxic species such as sulfides, metals and natural radionuclides due to the convective seawater circulation inside the oceanic crust and its interaction with basaltic or ultramafic host rocks. However, data on radionuclides in biota from such environment are very limited. An investigation was carried out on tissue partitioning of 210Po and 210Pb, two natural radionuclides within the 238U decay chain, in Bathymodiolus azoricus specimens from the Mid-Atlantic Ridge (Menez Gwen field). These two elements showed different distributions with high 210Pb levels in gills and high 210Po levels in both gills and especially in the remaining parts of the body tissue (including the digestive gland). Various factors that may explain such partitioning are discussed. However, 210Po levels encountered in B. azoricus were not exceptionally high, leading to weighted internal dose rate in the range 3 to 4 μGy h− 1. These levels are slightly higher than levels characterizing coastal mussels (~ 1 μGy h− 1).  相似文献   
68.
69.
In the past decade, much of the research on adolescent development has focused on the transitions that define and shape the experiences of adolescents. Several models are identified that have been useful in predicting and understanding behavioral and affective change at transitions, in particular, transitions occurring from middle childhood through adolescence. Some models are specific to particular transition points ( such as pubertal development ), whereas others may be applied more generally, even if they have only been tested for at a single transition. Of importance is how well the data fit each model and whether continuity in outcomes is predicted by the models across different transitions. Examples highlight research on how a specific transition, event, or ecological niche influences adolescent behavior and affect. To understand which individuals are affected by transitions and how transitions are navigated, more specific models are needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
70.
Strategy use and its impact on standardized reading test performance were investigated. High school students were randomly assigned to 2 groups, standardized test and main idea, with separate control and think-aloud conditions. In the standardized think-aloud group, students thought aloud while taking a portion of a reading test, consisting of passages accompanied by several questions each. In the main idea conditions, students read the same passages with the lower level questions removed and answered a single multiple-choice question about the main idea of each passage, having been told that the task was not a test. Both groups used strategies, and students in the standardized test condition made significantly greater use of strategies than students in the main idea condition. Significant between-group differences were found in use of rereading. In comparisons between the think-aloud and control conditions, thinking aloud was found to have a significant detrimental effect on students' ability to identify passage main ideas. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号